Micro X-ray Computed Tomography (CT) Scanning & Analysis

Exponent employs CT analysis in many projects on a wide variety of objects, often requiring no sample preparation or modification. Exponent owns and operates CT systems at multiple offices, with varied capabilities in terms of sample size and scan quality/resolution. In addition to 3-D imaging, Exponent has multiple consultants with experience in image processing and advanced analysis of CT data sets. 

Micro X-ray Computed Tomography (CT) is a nondestructive technique for visualizing object interiors. It is currently used to examine a wide range of materials, including rock, bone, ceramic, metal, and soft tissue. Most people are familiar with the use of CAT scans in medical applications where it is used to distinguish between different materials and provide a three-dimensional perspective of an object’s interior.

Micro CT differs from conventional medical CAT-scanning in its ability to resolve details as small as a few micrometers in size (i.e. less than 0.001 inches), even when imaging objects composed of high density materials. Although higher atomic-numbered materials (i.e. gold) scatter X-ray’s much more effectively than lower, or "lighter," materials (i.e., carbon), advances in equipment and image processing techniques now allow for high-resolution data sets with a variety of materials, shapes, and sizes. In order to produce CT images, multiple X-ray images are taken as the object is rotated around a central rotation axis. These separate "projections" of the object are then used to mathematically determine the relative density of the object at different locations in the plane(s) of interest. This imaging process is then repeated for each desired slice of the object until a stack of images has been produced representing the internal structure of the object. This data set can then be exported as 2-D stacks of images in any plane desired, or studied and exported in 3-D images or videos. 



Figure 1. An X-ray projection image (left) and a 2-D slice (right) taken from CT scan data of a 12” laptop.

Figure 2. Example CT data analysis showing (a) solder ball grid array (BGA) profiles that may indicate process problems, (b) dendrite formation inside of electronics, (c) 3D component visualization and (d) zoom and 3D visualization of component cracking.

Figure 3. Two-dimensional (top) and 3-D views (bottom) of an 18650-sized lithium-ion cell, showing proper alignment (overlap) of negative to positive electrodes in the cell construction.

Figure 4. A 3-D image of a 4 mm diameter Zinc-air battery (left; cropped), with advanced analysis of particle size using MATLAB. The particle sizes are color-coded based on volume (middle), with a histogram demonstrating the distribution (right plot).

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